Javascript array copying, concat vs slice, which one is better?

Question

there are two different ways to copy a array, using Array.concat or Array.slice,

for example:

var a = [1, 2, 3],

    c1 = [].concat(a),

    c2 = a.slice(0);

which way is better?

`arr.slice()` might be faster , just benchmark it .http://jsperf.com/duplicate-array-slice-vs-concat/3 — AllTooSir, Jul 23 '13 at 07:11
check this out http://jsperf.com/duplicate-array-slice-vs-concat/3 slice is faster — Satpal, Jul 23 '13 at 07:11
http://stackoverflow.com/questions/3978492/javascript-fastest-way-to-duplicate-an-array-slice-vs-for-loop For all I've read, slice is faster. — Andrei Neculai, Jul 23 '13 at 07:11

Alnitak · Accepted Answer · 2018-01-19T08:20:32.343

14

For clarity, you should use the method that is the documented method of taking a copy of an array (or portion thereof):

var c2 = a.slice(0);

On any decent browser the performance difference will be negligible, so clarity should be the deciding factor.

edited Jan 19 '18 at 08:20

answered Jul 23 '13 at 07:24

Alnitak

Documented where? – ericsoco Jan 19 '18 at 05:14
@ericsoco https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/slice - _"The `slice()` method returns a shallow copy of a portion of an array into a new array object selected from `begin` to `end` (`end` not included). The original array will not be modified."_ – Alnitak Jan 19 '18 at 08:19

David Pärsson · Answer 2 · 2013-07-23T07:18:21.733

5

In terms of performance, the difference between the two options are minimal, according to a jsperf.com test.

edited Jul 23 '13 at 07:18

answered Jul 23 '13 at 07:13

David Pärsson

2 Answers2